Flexible cross-correlated (C²) imaging method for the modal content characterization in a broad range of wavelengths

We demonstrate a flexible cross-correlated (C²) imaging method in the time domain by application of a tunable and highly flexible light source. An advantage of the flexible C² method is shown by characterization of the step-index fiber (SMF28) over a broad range of wavelengths from 870nm to 1090nm and by the modal analysis of the distributed modal filtering (DMF) rod fiber within a wavelength range from 1050nm to 1090nm. Also, the influence of the spectral shape and bandwidth on the imaging trace is investigated by deliberately adjusting the input spectrum of the light source. The modal intensity as well as the phase distribution are extracted by the alternative method of 2D FT filtering. Being exceptionally tunable the flexible C² method gives an ability to adapt the system's parameters in a desired manner satisfying even measurements of very specific fiber designs opening up new possibilities for advanced modal characterization of fibers over broad range of wavelengths.